"""外部功率计采样后端（示例）"""

from __future__ import annotations
from typing import Optional
import os

from .base import PowerBackend


class ExternalMeterBackend(PowerBackend):
    """外部功率计采样（示例）"""
    
    def __init__(self):
        self._connection = None
    
    @staticmethod
    def is_available() -> bool:
        # 检查是否配置了外部功率计
        return os.environ.get("POWER_METER_HOST") is not None
    
    def init(self, device_id: int = 0) -> bool:
        try:
            # 示例：通过 HTTP 连接到功率计
            host = os.environ.get("POWER_METER_HOST", "localhost:8080")
            # self._connection = connect_to_power_meter(host)
            return False  # 占位实现
        except:
            return False
    
    def sample(self) -> Optional[float]:
        # 从功率计读取数据
        # power_W = self._connection.read_power()
        return None  # 占位实现
    
    def cleanup(self):
        if self._connection:
            # self._connection.close()
            pass
    
    def get_name(self) -> str:
        return "external_meter"

